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Math Expert
Joined: 02 Sep 2009
Posts: 50627

Question Stats:
80% (01:55) correct 20% (02:21) wrong based on 160 sessions
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Math Expert
Joined: 02 Sep 2009
Posts: 50627

Re M2320
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16 Sep 2014, 00:19



Intern
Joined: 17 May 2016
Posts: 29

Re: M2320
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19 Dec 2016, 09:08
Hi,
Is it possible to calculate it algebraically ?
I get stuck with two unknown, even if I know that is quicker to back solve, I do not understand why it is not solvable ?
Many thanks in advance for your kind help



Math Expert
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Posts: 50627

Re: M2320
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19 Dec 2016, 09:18



Intern
Joined: 17 May 2016
Posts: 29

Re: M2320
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20 Dec 2016, 01:53
I mean that if I set up the table, I get the following :
FIRST MOVE : \(r*(t+\frac{1}{2}) = 60\) 2ND MOVE : \((r+20)*t = 60\)
Then, since they are equal : \(r*(t+\frac{1}{2}) = (r+20)*t\) \(rt + \frac{r}{2} = rt + 20t\) \(r = 40t\)
Then I have a problem with the unit, I know that 40 is the good value but I am not supposed to express a rate and a time, only a rate.
thanks in advance for your help



Manager
Joined: 23 Jan 2016
Posts: 194
Location: India
GPA: 3.2

Re: M2320
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06 Apr 2017, 21:33
Could you please share some links to questions similar to this? Thank you.



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06 Apr 2017, 23:29



Manager
Joined: 28 Dec 2016
Posts: 88
Location: United States (IL)
Concentration: Marketing, General Management

Re: M2320
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09 Apr 2018, 11:05
For those of you wanting to set up an equation and solve it w/o plugging in, I can chime in to help. Since traveling at 20kmh faster saves 1/2 hour, we can say that: 60/R  60/(R+20) = 1/2, which is basically saying: (Time at Reg Speed)  (Time +20kmh faster) = (30 mins)
Solving, we get: (R+60)(R40)=0 R= 60, 40
Rate can not be negative, therefore, 40 is the winner.










